Molding processes for making multilayer containers of different materials

Abstract

An improved method of pulp or pressure molding a multilayer container is disclosed wherein the inner layer consists of fused water dispersible polyolefin fibers whereas the outer layer consists of a mixture of cellulosic fibers bonded together by fused water dispersible polyolefin fibers. The containers are useful because the polyolefin layer is resistant to the passage of liquid such as lubricating oils and semi-solids such as greases while the mixed layer of cellulosic fibers and the polyolefin fiber supplies sufficient strength to permit the stacking of the containers when filled.

The invention claimed is: 
     
       1. A pulp molding process for making a multilayer container comprising: (a) forming at least one shaped inner layer consisting of water dispersible polyolefin fibers from a water slurry of said fibers on a container forming means wherein the amount of the fibers is in the range of about 16 weight % to about 50 weight % of the total weight of resulting container;   (b) forming juxtaposed to the inner shaped layer at least one outer layer of a mixture of cellulosic fibers and polyolefin fibers form a water slurry of said mixture of fibers wherein the amount of the fibers in the mixture is in the range of about 10 weight % to about 90 weight %;   (c) removing resulting multilayer formed shape container from the forming means and removing any remaining water contained in the multilayer formed shape container; and   (d) subjecting the removed multilayer formed shape container to sufficient heat and pressure to fuse the polyolefin fibers of the inner layer into a liquid barrier and to fuse the polyolefin fibers of the cellulosic layer to the inner layer.   
     
     
       2. Process according to claim 1 wherein the polyolefin is selected from the group consisting of low density polyethylene, medium density polyethylene, high density polyethylene, crystalline polypropylene, poly-1-butene and poly-4-methyl-1-pentene. 
     
     
       3. Process according to claim 1 wherein only two layers are formed. 
     
     
       4. Process according to claim 3 wherein the polyolefin is selected from the group consisting of low density polyethylene, medium density polyethylene, high density polyethylene, crystalline polypropylene, poly-1-butene and poly-4-methyl-1-pentene. 
     
     
       5. Process according to claim 4 wherein the amount of fibers in the mixture is in the range of about 20% to about 50%.